Name: ______________________________________
Date: ________________________
Student Exploration: Building DNA
Vocabulary: double helix, DNA, enzyme, mutation, nitrogenous base, nucleoside,
nucleotide, replication
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
DNA is an incredible molecule that forms the basis of life on Earth. DNA molecules
contain instructions for building every living organism on Earth, from the tiniest
bacterium to a massive blue whale. DNA also has the ability to replicate, or make
copies of itself. This allows living things to grow and reproduce.
1. Look at the DNA molecule shown at right. What does it look like?
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This shape is called a double helix.
2. Based on this picture, how do you think a DNA molecule makes a
copy of itself? (Hint: Look at the bottom two “rungs” of the ladder.)
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Gizmo Warm-up
The Building DNA Gizmo™ allows you to construct a DNA
molecule and go through the process of DNA replication.
Examine the components that make up a DNA molecule.
1. What are the two DNA components shown in the Gizmo?
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2. A nucleoside has two parts: a pentagonal sugar
(deoxyribose) and a nitrogenous base (in color). When a
nucleoside is joined to a phosphate, it is called a nucleotide.
How many different nitrogenous bases do you see?
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Note: The names of these nitrogenous bases are adenine (red), cytosine (yellow),
guanine (blue), and thymine (green).
Activity A:
Get the Gizmo ready:
 If necessary, click Reset to start the
Build a DNA
building process.
molecule
Question: What is the structure of DNA?
Left side
1. Build: Follow the steps given in the
Gizmo to construct a molecule of DNA.
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(Note: For simplicity, this DNA molecule
is shown in two dimensions, without the
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twist.)
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Stop when the hint reads: “The DNA
molecule is complete.” In the spaces at
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right, list the sequence of nitrogenous
bases on the left-hand side of the DNA
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molecule and the right-hand side.
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2. Take a picture: Click the camera ( ) to
take a snapshot of your DNA molecule.
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Right-click the image and select Copy
Image. Paste the image into a blank
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document, and label this image “Original
DNA molecule.”
Right side
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3. Explain: Describe the structure of the DNA molecule you made.
A. What makes up the sides of the DNA molecule?______________
B. What makes up the “rungs” of the DNA molecule?_____________
4. Fill in: Write the name of the nitrogenous base that joins to each of the
bases below:
Adenine (A) joins to ____________Thymine (T) joins to __________
Cytosine (C) joins to ____________Guanine (G) joins to __________
5. Practice: The left side of a DNA molecule is shown.
Draw a complementary right side of the molecule.
Activity B:
DNA
replication
Get the Gizmo ready:
 Be sure the hint reads: “The DNA molecule
is complete.” If not, click Reset and build a
new DNA molecule.
Question: How does DNA make a copy of itself?
1. Observe: An enzyme is a protein that facilitates certain cell processes.
Click Release enzyme to release DNA helicase. What does this
enzyme do to the DNA molecule?
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2. Observe: Click Release enzyme to release DNA polymerase.
A. Notice that two groups of Nucleotides appear on the right. What
are the three parts of a nucleotide? _________________,
_________________, _________________
B. Drag one of the nucleotides to a corresponding nitrogenous base
on one of the two strands. What is the role of DNA polymerase in
this process?
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3. Build: Complete the two molecules of DNA by dragging nucleotides to
their corresponding locations. When you have finished, compare the two
completed daughter DNA molecules.
What do you notice about the two molecules?
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4. Take a picture: Click the camera to take a snapshot of the DNA
molecules, and paste the image into your document. Label this image
“Daughter DNA molecules.”
How do these molecules compare to the original?
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5. Think and discuss: Why is DNA replication such an important process?
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6. Extend your thinking: Sometimes errors called mutations occur during
DNA replication. What are some of the possible consequences of
mutations?
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